Power amplifier circuit

Abstract

There is provided a power amplifier circuit with improved operation speed of the protection function against overcurrent or overvoltage. The power amplifier circuit includes an amplifier configured to amplify a radio frequency signal and output the radio frequency signal, a bias current supply circuit configured to supply a bias current to the amplifier, a detection circuit configured to detect whether the current or voltage of the amplifier is equal to or greater than a predetermined threshold; and a draw circuit configured to, when the detection circuit detects that the current or voltage is equal to or greater than the predetermined threshold, draw at least a part of the bias current supplied to the amplifier.

The invention claimed is: 
     
       1. A power amplifier circuit comprising:
 an amplifier configured to amplify a radio frequency signal and to output an amplified radio frequency signal; 
 a bias current supply circuit comprising a first transistor configured to supply a bias current to the amplifier; 
 a detection circuit configured to detect whether a current or a voltage of the amplifier is equal to or greater than a predetermined threshold; and 
 a second transistor connected between the first transistor and ground, 
 
       wherein a collector or a drain of the second transistor is connected to an emitter or a source of the first transistor, and an emitter or a source of the second transistor is connected to ground. 
     
     
       2. The power amplifier circuit according to  claim 1 , further comprising a collector current supply circuit configured to:
 supply a current to a collector of the first transistor, and 
 when the detection circuit detects that the current or the voltage of the amplifier is equal to or greater than the predetermined threshold, stop the current supply to the collector of the first transistor. 
 
     
     
       3. The power amplifier circuit according to  claim 1 , further comprising:
 a collector current supply circuit configured to supply a current to a collector of the first transistor, wherein the collector current supply circuit comprises:
 a current mirror circuit comprising a third transistor and a fourth transistor; 
 a fifth transistor connected between a supply voltage and the third and fourth transistors; and 
 a sixth transistor connected between the third transistor or the fourth transistor, and ground. 
 
 
     
     
       4. The power amplifier circuit according to  claim 3 , further comprising:
 an inverter connected to the collector current supply circuit, 
 
       wherein a base or a gate of the fifth transistor is connected to an output terminal of the inverter, and
 wherein a base or a gate of the sixth transistor is connected to an input terminal of the inverter. 
 
     
     
       5. The power amplifier circuit according to  claim 1 , further comprising a second bias current supply circuit configured to:
 supply a second bias current to a base of the first transistor; and 
 when the detection circuit detects that the current or voltage of the amplifier is equal to or greater than the predetermined threshold, stop supplying the second bias current. 
 
     
     
       6. The power amplifier circuit according to  claim 1 , further comprising:
 a second bias current supply circuit configured to supply a second bias current to a base of the first transistor, wherein the second bias current supply circuit comprises:
 a current mirror circuit comprising a seventh transistor and an eighth transistor; 
 a ninth transistor connected between a supply voltage and the seventh and eighth transistors; and 
 a tenth transistor connected between the seventh transistor or the eighth transistor, and ground. 
 
 
     
     
       7. The power amplifier circuit according to  claim 6 , further comprising:
 an inverter connected to the second bias current supply circuit, 
 
       wherein a base or a gate of the ninth transistor is connected to an output terminal of the inverter, and
 wherein a base or a gate of the tenth transistor is connected to an input terminal of the inverter. 
 
     
     
       8. The power amplifier circuit according to  claim 1 , wherein the detection circuit comprises:
 a resistor configured to detect the current or the voltage of the amplifier, and 
 a comparison circuit configured to compare the current or the voltage detected by the resistor to the predetermined threshold, and to output a comparison result. 
 
     
     
       9. The power amplifier circuit according to  claim 1 , wherein the detection circuit comprises:
 a replica transistor having a collector configured to receive an inflow current corresponding to a current of the amplifier; 
 a replica resistor configured to detect the inflow current of the replica transistor; and 
 a second comparison circuit configured to compare the inflow current of the replica transistor and detected by the replica resistor to a predetermined second threshold, and to output a comparison result. 
 
     
     
       10. The power amplifier circuit according to  claim 1 , wherein the amplifier comprises a heterojunction bipolar transistor. 
     
     
       11. The power amplifier circuit according to  claim 1 , further comprising:
 a second amplifier configured to amplify a second radio frequency signal and to output a second amplified radio frequency signal; 
 a third bias current supply circuit configured to supply a third bias current to the second amplifier; 
 a second detection circuit configured to detect whether a current or a voltage of the second amplifier is equal to or greater than a predetermined second threshold; and 
 a second draw circuit configured to, when the second detection circuit detects that the current or the voltage of the second amplifier is equal to or greater than the predetermined second threshold, draw at least a part of the third bias current supplied to the second amplifier. 
 
     
     
       12. A power amplifier circuit comprising:
 an amplifier configured to amplify a radio frequency signal and to output an amplified radio frequency signal; 
 a bias current supply circuit comprising a first transistor configured to supply a bias current to the amplifier; 
 a detection circuit configured to detect whether a current or a voltage of the amplifier is equal to or greater than a predetermined threshold; and 
 a draw circuit configured to, when the detection circuit detects that the current or the voltage is equal to or greater than the predetermined threshold, draw at least a part of the bias current supplied to the amplifier, and 
 a collector current supply circuit configured to:
 supply a current to a collector of the first transistor, and 
 when the detection circuit detects that the current or the voltage of the amplifier is equal to or greater than the predetermined threshold, stop the current supply to the collector of the first transistor. 
 
 
     
     
       13. The power amplifier circuit according to  claim 12 , wherein the first transistor is configured to supply the bias current to the amplifier from an emitter or a source of the first transistor. 
     
     
       14. The power amplifier circuit according to  claim 13 , wherein the draw circuit comprises a second transistor, and a collector or a drain of the second transistor is connected to the emitter or the source of the first transistor.